Elevated ventricular filling pressures ultimately result in systemic and pulmonary venous congestion and edema, and are thus largely responsible for the manifestations of congestive heart failure. The goal of this research proposal is to assess the role of incomplete myocardial relaxation and ventricular viscoelastic properties in the development of elevated ventricular filling pressures. In particular, the applicant proposes: (a) to refine and assess in detail methodology relating to the detection of incomplete myocardial relaxation in man, (b) to pursue recent observations made by the applicant and his co-workers that under certain circumstances incomplete myocardial relaxation may be pharmacologically reversible.